When you buy a house, chances are you’re going to find at least a few incomprehensible decisions made by your home’s previous occupant. When those decisions involve important infrastructure—what look like stopgap repairs, or projects that seem like temporary fixes that became permanent over time—the urge to just rip them out and do them over the right way is often overwhelming. “What were they thinking?” you might wonder as you swing that sledgehammer.

And then, disaster. You remove an oddly placed planter in your backyard that’s ruining the layout, only to discover it was diverting water from your foundation—and now you have a flood. You find a basement window well covered in ugly, thick plastic, which you tear out to replace with a more attractive mesh—and a few months later a small jungle is growing in that well. Assuming previous owners were dumb or lazy is an easy way to make a lot more problems for your house. The best way to defend against this is second-order thinking, or what’s known as Chesterton’s Fence.

What is “Chesterton’s Fence”?

First-order thinking is simple stuff: You conceptualize an action and an immediate consequence. Consider that weird planter: The first-order thought is, I’ll remove that planter and my yard will look better. Second-order thinking is more abstract, and takes into account where the consequence of that action will lead—sometimes called the “consequences of the consequences.” The second-order thought asks: What else happens if I remove the planter? Will the water drainage shift? Will something be exposed that needs to be covered up? Will I disturb an ancient grave and unleash evil forces on my home?

The concept of Chesterton’s Fence wraps this concept up in a mental exercise. The concept comes from G. K. Chesterton’s book of essays, The Thing: Why I Am a Catholic, published in 1929. In it he describes someone coming across a gate across a road that seems to serve no purpose. One sort of “reformer,” he argues, assumes that if he can’t see the purpose there isn’t any purpose, and removes the gate. A “more intelligent” person won’t do anything until they can understand why it was put there in the first place.

Understand why something was done before you do anything about it

The idea of understanding why something was done before you remove or reverse it is key if you want to avoid home renovation disasters. Homeowners often make quick, DIY repairs that become permanent—because they work, despite not being the correct material or not using the correct techniques. And that original homeowner might be the only person who remembers the why of something.

Consider the dripping valve in an unheated garage. You buy a house and discover that a loose valve in the garage is always dripping a small amount of water. It’s an easy fix, and you feel very capable and handy. And then a few weeks later the pipe freezes and bursts, because the previous homeowner learned to just let it drip all the time. Taking a moment to stipulate that the drip might not have been negligence or ignorance and asking yourself why it was left loose might have led you to at least investigate the reason—and possibly saved you a lot of trouble and money.

Next time you notice some strange decision made by a previous owner in your house, don’t immediately suit up and start ripping the offending bit. Stop and do some second-order thinking, asking yourself why the decision was made in the first place. Only when you understand that can you safely proceed with your own plans. Doing this will save you a lot of time and trouble over the years.